/*
* Copyright (C) 2020  钟先耀
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*/
/*    $OpenBSD: ieee80211_amrr.c,v 1.12 2019/02/24 09:36:28 stsp Exp $    */

/*-
 * Copyright (c) 2006
 *    Damien Bergamini <damien.bergamini@free.fr>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/socket.h>

#include <net/if.h>
#include <net/if_media.h>

#include <netinet/in.h>
#include <netinet/if_ether.h>

#include <net80211/ieee80211_var.h>
#include <net80211/ieee80211_priv.h>
#include <net80211/ieee80211_amrr.h>

#define is_success(amn)    \
    ((amn)->amn_retrycnt < (amn)->amn_txcnt / 10)
#define is_failure(amn)    \
    ((amn)->amn_retrycnt > (amn)->amn_txcnt / 3)
#define is_enough(amn)        \
    ((amn)->amn_txcnt > 10)
#define reset_cnt(amn)        \
    do { (amn)->amn_txcnt = (amn)->amn_retrycnt = 0; } while (0)

static inline int
is_min_rate(struct ieee80211_node *ni)
{
    return (ni->ni_txrate == 0);
}

static inline int
is_max_rate(struct ieee80211_node *ni)
{
    return (ni->ni_txrate == ni->ni_rates.rs_nrates - 1);
}

static inline void
increase_rate(struct ieee80211_node *ni)
{
    ni->ni_txrate++;
}

static inline void
decrease_rate(struct ieee80211_node *ni)
{
    ni->ni_txrate--;
}

void
ieee80211_amrr_node_init(const struct ieee80211_amrr *amrr,
    struct ieee80211_amrr_node *amn)
{
    amn->amn_success = 0;
    amn->amn_recovery = 0;
    amn->amn_txcnt = amn->amn_retrycnt = 0;
    amn->amn_success_threshold = amrr->amrr_min_success_threshold;
}

/*
 * Update ni->ni_txrate.
 */
void
ieee80211_amrr_choose(struct ieee80211_amrr *amrr, struct ieee80211_node *ni,
    struct ieee80211_amrr_node *amn)
{
#define RV(rate)    ((rate) & IEEE80211_RATE_VAL)
    int need_change = 0;

    if (is_success(amn) && is_enough(amn)) {
        amn->amn_success++;
        if (amn->amn_success >= amn->amn_success_threshold &&
            !is_max_rate(ni)) {
            amn->amn_recovery = 1;
            amn->amn_success = 0;
            increase_rate(ni);
            DPRINTF(("increase rate=%d,#tx=%d,#retries=%d\n",
                RV(ni->ni_rates.rs_rates[ni->ni_txrate]),
                amn->amn_txcnt, amn->amn_retrycnt));
            need_change = 1;
        } else {
            amn->amn_recovery = 0;
        }
    } else if (is_failure(amn)) {
        amn->amn_success = 0;
        if (!is_min_rate(ni)) {
            if (amn->amn_recovery) {
                amn->amn_success_threshold *= 2;
                if (amn->amn_success_threshold >
                    amrr->amrr_max_success_threshold)
                    amn->amn_success_threshold =
                        amrr->amrr_max_success_threshold;
            } else {
                amn->amn_success_threshold =
                    amrr->amrr_min_success_threshold;
            }
            decrease_rate(ni);
            DPRINTF(("decrease rate=%d,#tx=%d,#retries=%d\n",
                RV(ni->ni_rates.rs_rates[ni->ni_txrate]),
                amn->amn_txcnt, amn->amn_retrycnt));
            need_change = 1;
        }
        amn->amn_recovery = 0;
    }

    if (is_enough(amn) || need_change)
        reset_cnt(amn);
#undef RV
}
